Current trends in studies of long-term plant community dynamics.
Current trends in studies of long-term plant community dynamics.
复制标题
长期植物群落动态研究的当前趋势。
作者：
J. C. Ritchie
长期植物群落动态进行了研究，通过分析的宏观和微观化石遗骸中发现的松散的湖沼和陆地沉积物，主要是晚第四纪和近代。保存在半干旱地区的食草鼠（Neotoma）中的大型植物化石提供了从最后一次冰期到今天的最具信息性的数据。除了少数例外，这些遗骸可以被鉴定为物种，它们代表了一个地点半径30-50米范围内植被物种组成的很大比例（>75%），它们可以通过加速器质谱放射性碳方法确定年代。大多数网站已被发现在干旱的美国西南部和最近作出了重大贡献，以了解物种组成的长期变化和变化的范围和海拔高度限制的物种。同样，对湖泊、沼泽和河流遗址中的宏体化石进行分析，可以利用分类学的精确性、小的来源区域和对样品进行精确放射性碳测年的潜力，提供湖泊、沼泽和河流生境的当地植被的详细重建。大量的文献报道这些调查主要涉及北方温带地区的网站，但最近的研究表明，热带和暖温带地区的方法的承诺。在过去的几十年中，作为重建森林轮胎历史的尝试的一部分，并结合其他分析（花粉，物理化学），调查过去的群落动态，使用沉积物中保存的微观炭分析显着增加。该方法的主要局限性是许多沉积物的年代控制不佳，源区的不确定性和有限的分类精度。另一方面，肉眼可见的木炭残留物通常可以在物种水平上进行鉴定，可以准确地确定年代，并容易确定来源地区。然而，具有跨越长时间连续时间间隔的高频率样本出现的地点是非常罕见的，正如非洲潮湿热带地区的一个显著例子所示。湖泊和沼泽沉积物的花粉分析有着悠久的历史，并产生了大量的文献。它作为一种工具，在使用它的三个主要领域-古气候学，文化史和植物群落动态中的弱点是众所周知的，并且在北方和南方的更远的地区增加。一、导言. 470第471章证据第487章第490章第一次见面
Long-term plant community dynamics has been investigated by analyses of macro- and microfossil remains found in unconsolidated limnic and terrestrial sediments, chiefly of Late-Quaternary and Recent age. Plant macrofossils preserved in packrat (Neotoma) midden sites in semi-arid regions have yielded the most informative data for the period between the lastest glacial to the present day. The remains can, with few exceptions, be identified to species level, they represent a large (>75%) proportion of the species composition of vegetation within a radius of 30-50 m of a site, and they can be dated by the accelerator mass-spectrometric radiocarbon method. Most sites have been found in the arid southwest of the United States and significant contributions have been made recently to understanding of long-term changes in species composition and shifts in range and elevational limits of species. Similarly, analysis of macrofossils in lake, mire and river sites can draw on the taxonomic precision, small source area and potential for precise radiocarbon dating of samples, to provide detailed reconstructions of the local vegetation of lacustrine, mire and fluvial habitats. The vast literature reporting these investigations deals with sites chiefly in northern temperate regions, but recent studies from tropical and warm-temperate regions show the promise of the approach. The use of analyses of microscopic charcoal preserved in sediments has increased significantly in the past few decades as part of attempts to reconstruct forest tire history and, when combined with other analyses (pollen, physical chemistry), to investigate past community dynamics. The major limitations of the method are poor chronological control in many sediments, uncertainties about source area and limited taxonomic precision. On the other hand, macroscopic remains of charcoal can usually be identified to species level, can be dated accurately and have readily defined source areas. However, sites with high frequencies of sample occurrence spanning long, continuous time intervals are very rare, as a remarkable example from the humid tropics of Africa illustrates. Pollen analysis of lake and mire sediments has a long history and has yielded a vast literature. Its weaknesses as a tool in the three main fields of interest where it is used - palaeoclimatology, cultural history and plant community dynamics are well known and increase in regions farther north and south of the boreal and Contents Summary 469 I. Introduction 470 II. Types of evidence 471 III. Problems and prospects 487 Acknowledgements 490 References 490.